people don't pay a premium just for a sea view, they pay it for all the location, lifestyle, facilities and infastructure that swansea offers.
things like access to nearby dentists, doctors, hospitals, leisure facilities, parks, beaches, marinas, swimming pools, gyms, nightlife, pubs, restaurants, post offices, banks, local shops, bigger shops, M4 motorway connection, mainline train station, regular bus service, schools, colleges, places for people to work like universities, hospitals, steelworks, industries and business parks, quality of life in terms of low crime, pace of life, scenery and community life.
you could buy a seaside property anywhere but it won't have what swansea offers.